# Thread: Issue implementing half bridge gate drive IR2110 in full bridge mode / High side not

1. ## Issue implementing half bridge gate drive IR2110 in full bridge mode / High side not

Hi Forum members,
Have a
The application requires switching on the motor for a specific period in either direction while the speed varies.
Have used 2 individual isolated High side floating supply vb1 & vb2 with respect to vs1 & vs2
Though the measured voltages at HIN pin is 4.5v the high side output is not switching on
Thank you
Arun kumar

2. Hi Arun,

It looks like the bootstrap capacitor is not sufficiently charged to turn on the high side output. What is the duty cycle? Make sure the low side is turned on long enough to charge the 47 uF bootstrap capacitor. You can also try reducing this capacitor to 22 uF.

Best regards,

Srivatsa

3. Hi Srivatsa,

Each bootstrap capacitor is charged through their individual isolated supply of 12 V @ 50mA.
The duty cycle varies between 1% to 99% at a fixed frequency of ~20 KHz.
Did tried varying the bootstrap capacitor with the following values 4.7/25, 10/25, 22/25, 47/25 & also 100/25
How to calculate the average current required to drive the MOSFETS for a specific drive frequency?
Have read a post on this forum saying
"average current drawn from 15V supply of I = Q x Fs,
where Q is the total gate charge of power MOSFET and Fs PWM frequency"
is it correct?

Thank you

Arun Kumar

4. Arun,

What is the status of SD pin? It is to be low for normal operation. See fig 1 in IR2110 datasheet.
Also, the driver has a undervoltage lock-out protection of 9.7 V. Check to make sure the 12V is stable under all conditions.
What is the HIN and LIN input voltage levels. For a VDD of 5 V, 3.3V level is required. See fig 12B in datasheet.

Yes. I = Qg * Fs can be used to calculate the drive current.

Best regards,

Srivatsa

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